There are two soldering processes which are generally accepted as useful in soldering components to printed-circuit boards. One is referred to as "wave soldering" and the other is referred to as "drag bath soldering".
In the "wave soldering" method, the printed-circuit board, to which components are to be attached by soldering, is carried over a wave of solder which is created by steady agitation of the fluid solder in a bath. A short but wide stationary wave of solder is created within the bath. The printed-circuit board is passed over the wave which splashes the board as it passes over the wave, touching it at its underside, in a line, which sweeps along the whole of its underside. The advantage of this method is, that a relatively small amount of heat is transferred to the printed-circuit board. A disadvantage of this method is that the fluid solder which has a tendency to oxidize, becomes oxided more quickly in view of the steady agitation.
In the "drag bath soldering" method, the bath of fluid solder remains relatively stationary. The printed-circuit board is dragged or pulled at low speed over the surface of the bath, where substantially its whole undersurface touches the fluid solder. At the end of its passage over the solder the board is pulled therefrom. As this occurs, small rearwardly directed slanted tails are drawn from each point of solder on the board. This is a serious disadvantage for the further processing of the soldered board.